JPH108975A - Intake system for crankcase supercharged 4-cycle engine - Google Patents

Abstract

(57) [Summary] [Purpose] An intake system for a crankcase supercharged four-stroke engine that enables supercharging of a crankcase at a predetermined load or more and that does not cause a decrease in charging efficiency over time at a predetermined load or less. To provide. In the intake device of a crankcase supercharged four-stroke engine 1 in which an air-fuel mixture introduced into a crank chamber 8 is compressed in the crank chamber 8 and guided to a combustion chamber S, the air-fuel mixture bypasses the crank chamber 8. And a three-way valve (switching means) 24 for switching an air-fuel mixture introduction path to the bypass pipe 27 side at a predetermined load or less. According to the present invention, at a predetermined load or less, the air-fuel mixture bypasses the crank chamber 8 and is directly supplied to the combustion chamber S. Therefore, the air-fuel mixture does not increase in temperature over time, and a stable output is derived. be able to.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake device of a crankcase supercharged four-stroke engine in which fresh air or air-fuel mixture introduced into a crankcase is compressed in the crankcase and guided to a combustion chamber.

[0002]

2. Description of the Related Art In recent years, a crankcase supercharged four-stroke engine for improving output has been proposed. In this crankcase supercharged four-stroke engine, fresh air or an air-fuel mixture is supplied to a piston in a crank chamber. The fuel is compressed by reciprocating motion and supplied (supercharged) to the combustion chamber to increase the charging efficiency, thereby improving the output.

Further, the present applicant has proposed a crankcase supercharged engine that compresses fresh air or air-fuel mixture in a crankcase by a swinging motion of a connecting rod.

[0004] In these crank chamber supercharged engines, compressed air in the passage from the crank chamber to the combustion chamber is supplied to the air upstream of the crank chamber through the bypass passage during idling in order to reduce fuel consumption. It has been considered that the supercharging is stopped by returning to the introduction path, and the amount of the air-fuel mixture or the amount of fresh air is reduced in accordance with the idling state.

[0005]

However, when the amount of the air-fuel mixture or the amount of fresh air in an operating state of a predetermined load or less is reduced by the above-described method, a small amount of the low-temperature air-fuel mixture or fresh air is introduced into the air. While a new suction is supplied to the passage, a supercharging work is performed by a piston or a connecting rod in the crank chamber, and the heated air-fuel mixture or fresh air is discharged to the air introduction passage through the bypass passage. The low-temperature mixture or fresh air mixes with the heated mixture or fresh air to increase the temperature, and the piston or the connecting rod performs supercharging work again in the crank chamber to further increase the temperature. A part of the heated air-fuel mixture or fresh air is partially supplied to the combustion chamber, but most of the air-fuel mixture or the fresh air is circulated through the bypass passage to the entrance to the air hall. For this reason, after opening the bypass passage under a predetermined load or less, the charging efficiency is reduced with the passage of time, and the output may be insufficient.

Further, the lubricating oil flows out of the crank chamber together with the fresh air or the air-fuel mixture compressed in the crank chamber and accumulates in the middle of the passage from the crank chamber to the combustion chamber, so that the consumption of the lubricating oil increases. There was also.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. It is an object of the present invention to enable supercharging of a crank chamber at a predetermined load or more, and to reduce the charging efficiency with the passage of time at a predetermined load or less. It is an object of the present invention to provide an intake device for a crankcase supercharged four-stroke engine that does not have any problem.

Another object of the present invention is to provide an intake system for a crankcase supercharged four-stroke engine which can suppress the outflow of lubricating oil from the crankcase and reduce the consumption of lubricating oil. It is in.

[0009]

According to a first aspect of the present invention, there is provided a crank chamber which compresses fresh air or air-fuel mixture introduced into a crank chamber and guides it to a combustion chamber. In an intake device for a supercharged engine, a bypass passage for introducing fresh air or air-fuel mixture to a combustion chamber by bypassing a crank chamber and a switching unit for switching an introduction path of fresh air or air-fuel mixture to the bypass passage side at least when idling is provided. It is characterized by having.

According to a second aspect of the present invention, in the first aspect of the present invention, the check valve is provided in the bypass passage so as to allow only the flow of fresh air or air-fuel mixture toward the combustion chamber. I do.

According to a third aspect of the present invention, in the first or second aspect, the switching means is driven by an actuator whose drive is controlled based on the engine speed or the throttle opening. It is characterized by the following.

According to a fourth aspect of the present invention, in the first, second, or third aspect of the present invention, the switching means includes a branch portion in which the bypass passage branches from a suction pipe for introducing fresh air or air-fuel mixture into a crankcase. Characterized by a three-way valve provided in the device.

The invention according to claim 5 is the invention according to claims 1, 2, 3
Alternatively, in the invention described in Item 4, a pressure accumulating chamber is provided in the middle of a pressurized suction pipe for guiding fresh air or air-fuel mixture compressed in the crank chamber to the combustion chamber.

Therefore, according to the present invention, when the load is equal to or less than the predetermined load, the fresh air or the air-fuel mixture is directly supplied to the combustion chamber, bypassing the crank chamber. And a stable output can be derived.

Further, under a predetermined load, fresh air or air-fuel mixture bypasses the crankcase, so that lubricating oil in the crankcase does not flow out of the crankcase together with fresh air or air-fuel mixture. It can be kept low.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view of a unit swing type engine unit showing the configuration of a crankcase supercharged four-stroke engine provided with an intake device according to the present invention. FIG. 2 is a connecting rod of the crankcase supercharged four-stroke engine. FIG. 3 is a cross-sectional perspective view showing a configuration of a supercharging mechanism, and FIG. 3 is a partial cross-sectional view showing a configuration of a merger portion of the intake device according to the present invention.

First, referring to FIG.
The schematic configuration of the cycle engine 1 will be described.
A unit swing type engine unit 100 is mounted on a scooter type motorcycle. The engine unit 100 has a front end supported by a bracket 102 on a vehicle body side by a pivot shaft 101 so as to be able to swing up and down, and a rear end provided with a rear end. It is suspended from the vehicle body via a cushion 103.

The crankcase supercharged four-stroke engine 1 is integrally incorporated in the unit swing type engine unit 100. The crankcase supercharged four-cycle engine 1 is an air-cooled single cylinder engine. hand,
A piston 4 is slidably fitted in a substantially horizontal direction in a cylinder 3 formed in the cylinder body 2.
The piston 4 is connected to a crankshaft 6 via a connecting rod 5. The crankshaft 6 is rotatably housed in a crankcase 8 formed in a crankcase 7, and its rotation is not shown. The power is transmitted to a rear wheel (not shown) via a transmission mechanism or the like.

The crankcase supercharged four-cycle engine 1 according to the present embodiment has a connecting rod supercharging mechanism in the crankcase 8. Here, the configuration of the connecting rod supercharging mechanism will be described with reference to FIG.

The connecting rod 5 has a small end connected to the piston 4 by a piston pin 9 and a large end connected to a crank web 11 by a crank pin 10. A cylindrical curved inner peripheral wall 7a is formed along the outer periphery, and a required pumping action is performed by moving the large end of the connecting rod 5 along the inner peripheral wall 7a with a small clearance.

The cylinder body 2 and the piston 4 have
Slope-shaped notch 2 to avoid interference with connecting rod 5
a, 4a are respectively formed, and concave side walls 2b, 4b are respectively formed on the same plane as the crank web 11, and these concave side walls 2b, 4b and the crank web 11 are connected to one side surface of the connecting rod 5 (FIG. 2 with a small clearance.

When the large end of the connecting rod 5 is moving along the inner peripheral wall 7a as shown in FIG. 1, the connecting rod supercharging mechanism moves the inside of the crank chamber 8 by the connecting rod 5 into the suction chamber A. And a compression chamber B, a type of positive displacement type that sucks the air-fuel mixture into the suction chamber A whose volume increases with the swinging movement of the connecting rod 5 and compresses the air-fuel mixture in the compression chamber B whose volume decreases. The crankcase 7 has a suction port 12 opening to a suction chamber A and a discharge port 13 opening to a compression chamber B.

On the other hand, as shown in FIG. 1, a cylinder head 14 attached to the cylinder body 2
5 and an exhaust passage 16 are formed, and an intake port and an exhaust port in which the intake passage 15 and the exhaust passage 16 open to the combustion chamber S are opened and closed at appropriate timing by an intake valve 17 and an exhaust valve 18, respectively. As a result, a required gas exchange is performed in the cylinder 3. The intake valve 17 and the exhaust valve 18 are connected to tappets 20, 2 driven by a cam 19a formed integrally with a cam shaft 19.
1 is operated to open and close, respectively.

Here, the configuration of the intake device according to the present invention will be described.

In FIG. 1, reference numeral 22 denotes an air cleaner which opens to the atmosphere through a suction port 22a. The air cleaner 22 is connected to a three-way valve 24 as switching means via a first suction pipe 23. In the middle of the first suction pipe 23, a carburetor 25 provided with a throttle valve whose opening degree is increased or decreased according to the accelerator position (that is, load) is provided.

A second suction pipe 26 and a bypass pipe 27 extend from the three-way valve 24, and the second suction pipe 26 is connected to the suction port 12 of the crankcase 7.

A first pressurized suction pipe 28 is connected to the discharge port 13 formed in the crankcase 7.
This first pressurized suction pipe 28 is connected to a merger 29. In the middle of the first pressurized suction pipe 28, the pressure accumulating chamber 3
0 is provided. In addition, a reed valve 31 is provided at a connection portion of the first pressurized suction pipe 28 to the discharge port 13 for preventing the air-fuel mixture pressurized in the crank chamber 8 from flowing back to the crank chamber 8 side. ing. Also, the first pressurized suction pipe 28
A plurality of cooling fins 28a are integrally provided on the outer periphery of the fin.

The bypass pipe 27 and the second pressurized suction pipe 32 are connected to the merger 29, and the second pressurized suction pipe 32 is connected to the cylinder head 14 Is connected to the intake passage 15 formed at the bottom. An exhaust pipe 33 is connected to the exhaust passage 16 formed in the cylinder head 14.

Here, the configuration of the merging unit 29 will be described in detail with reference to FIG.

Inside the main body 29a of the merger 29, there is formed a nozzle portion 29b which throttles the high-pressure mixture stored in the pressure accumulating chamber 30 and flows the mixture to the second pressurized suction pipe 32. A ring-shaped chamber 29c is provided around the nozzle 29a.
Is formed, and a connection pipe 29d connected to the chamber 29c is protruded from a part of the outer periphery of the main body 29a. The bypass pipe 27 is connected to the connection pipe 29d with a reed valve 34 interposed therebetween. The reed valve 34 allows only the flow of the air-fuel mixture flowing through the bypass pipe 27 in the direction of the merger 29 (that is, prevents the backflow in the direction of the three-way valve 24).

The three-way valve 24 selectively flows the air-fuel mixture formed in the carburetor 25 to either the second suction pipe 26 or the bypass pipe 27 or to both of them. This is provided with a switching vane 37 which is rotated around an axis 36 by an actuator 35 such as a servomotor. The drive of the actuator 35 is controlled by an engine control device (hereinafter abbreviated as ECU) 38 as follows.

That is, the ECU 38 determines the operating state of the engine 1 based on the engine speed signal a or the throttle opening signal b input thereto. When the engine 1 is in the idling state, the ECU 38 The control signal c is output, the actuator 35 is driven to switch the three-way valve 24, and the switching vane 27 of the three-way valve 24 is switched.
Is switched from the state shown by the solid line to the state shown by the chain line in FIG.
7, the mixture is bypassed through the crank chamber 8 and flows into the bypass pipe 27.

When the ECU 38 determines that the operation state of the engine 1 is not the idling state, the ECU 38 outputs a control signal c to the actuator 35 and drives the actuator 25 to switch the three-way valve 24 in the same manner as described above. The switching vane 37 of the three-way valve 24 is switched from the state shown by the chain line in FIG.
Is closed, the second suction pipe 26 is opened, and the mixture flows to the second suction pipe 26 side.

Further, in a high-rotation, high-load operation state, the switching vane 37 is held at an intermediate position between the two positions, and the suction pipe 23 between the carburetor 25 and the three-way valve 24 expands downstream. Thus, it is possible to supply a sufficient mixture to both the suction pipe 26 and the bypass pipe 27.

Next, the lubricating oil supply system of the crankcase supercharged engine 1 will be described.

The lubricating oil stored in the oil tank 39 shown in FIG.
The pressure is increased by the oil pump 41 and supplied to sliding parts such as the piston 4, the crankshaft 6, the crankpin 10 via the delivery pipe 42, and used for lubrication of these sliding parts. The lubricating oil used for lubrication and accumulated at the bottom of the crankcase 7 is recovered by the oil pump 41 via the check valve 43 and the oil drain return pipe 44.
It is used for lubrication of each sliding part repeatedly.

Next, the operation of the crankcase supercharged engine 1 will be described.

When the crankcase supercharged four-cycle engine 1 is driven, the ECU 38 determines the operating state of the engine 1 based on the engine speed or the throttle opening as described above, and according to the operating state of the engine 1, The actuator 35 is controlled.

When the operating state of the engine 1 is not in the idling state, the switching vane 37 of the three-way valve 24 is connected to the bypass pipe 2 as shown by a solid line in FIG.
7 to close and open the second suction pipe 26, the carburetor 2
5 flows from the first suction pipe 23 to the second suction pipe 26,
2 is introduced into the suction chamber A in the crank chamber 8 and is compressed by the connecting rod supercharging mechanism every rotation of the crankshaft 6 and discharged from the compression chamber B to the discharge port 13 as described above. Then, the high-pressure mixture discharged to the discharge port 13 is:
Flows through the first pressurized suction pipe 28 through the reed valve 31,
After being cooled by heat radiation from the cooling fins 28 a on the way, the cooling fins 28 a are stored in the pressure accumulating chamber 30.
At the same time as the intake valve 17 is opened during the intake stroke of the engine 1, the air is supplied (supercharged) from the accumulator 30 into the cylinder 3 through the second pressurized suction pipe 32 and the intake passage 15.

As described above, supply into the cylinder 3 (supercharging)
The resulting mixture is compressed in a subsequent compression stroke and then provided for combustion in a combustion chamber S, and a part of heat energy generated by the combustion is taken out as rotational power of the crankshaft 6. In addition, cylinder 3
The exhaust gas generated inside the exhaust valve 1
As soon as 8 is opened, it is discharged into the atmosphere via the exhaust passage 16 and the exhaust pipe 33.

As described above, except during idling, the air-fuel mixture is compressed in the crank chamber 8 and supercharged into the cylinder 3, so that the charging efficiency of the air-fuel mixture is increased and the output of the engine 1 is increased. Since the air-fuel mixture is cooled while flowing through the first pressurized suction pipe 28, its density is increased, which also increases the charging efficiency.

On the other hand, when the ECU 38 determines that the operation state of the engine 1 is the idling state, the drive of the actuator 35 is controlled to switch the three-way valve 24 as described above. Then, the switching vane 37 of the three-way valve 24 closes the second suction pipe 26 and opens the bypass pipe 27 as shown by a chain line in FIG. 1, so that the air-fuel mixture flows into the bypass pipe 27 and flows through the crank chamber 8. Since the air-fuel mixture is directly supplied from the merging device 29 and the second pressurized suction pipe 32 to the cylinder 3 (combustion chamber S) by bypass (that is, without being compressed by the connecting rod supercharging mechanism), the supercharge of the air-fuel mixture is performed. Is not done.

Since the air-fuel mixture is not introduced into the crank chamber 8 during idling as described above, a low-temperature air-fuel mixture is always supplied to the combustion chamber S. Furthermore, the crankcase 8
In this case, since the pressure between the three-way valve 24 and the reed valve 31 becomes a negative pressure, the supercharging work by the connecting rod supercharging mechanism is not performed. Therefore, the energy loss due to the supercharging work is suppressed to be small, and the fuel efficiency is improved.

Since the air-fuel mixture bypasses the crankcase 8 during idling, the lubricating oil in the crankcase 8 does not flow out of the crankcase 8 together with the air-fuel mixture and accumulates in the accumulator chamber 30. Consumption can be kept low.

When the ECU 38 determines that the operating state of the engine 1 is a high rotation / high load load, the ECU 38 drives the actuator 35 to maintain the switching vane 37 at the intermediate position as described above. Flows toward the suction pipe 26, and is pressurized in the crank chamber 8, so that the pressurized suction pipe 28 and the accumulator 30
And flows into the combustion chamber S during the intake stroke of the engine 1. When the air-fuel mixture stored in the upstream part of the merging device 29 flows in the direction of the combustion chamber S, the air-fuel mixture is supplied to the combustion chamber S even if the air-fuel mixture passes through the bypass pipe 27 in order to make the chamber 29c a negative pressure. And the filling efficiency is improved.

The suction chamber A and the compression chamber B of the crank chamber 8
The on-off valve 20 controlled to be opened and closed by the ECU 38 in the middle
1 may be connected to each other by a second bypass passage 200 provided therein. When the engine 1 is in the idling state, the on-off valve 201 is opened in accordance with the switching vane 37 closing the second suction pipe 26, and the on-off valve 201 is closed in other operating states. As a result, the air-fuel mixture circulates between the suction chamber A and the compression chamber B of the crank chamber 8 and the temperature rises.
While the low-temperature air-fuel mixture is supplied directly from the bypass pipe 27 to the combustion chamber S, when the accelerator position is changed from the idling state to the large load side, the temperature in the crank chamber 8 is not negative because the pressure in the crank chamber 8 is not negative. Although high, the supercharged air-fuel mixture is immediately switched to the combustion chamber S with the switching of the switching valve 37.
Can be supplied to Thus, the acceleration response of the engine 1 is not impaired.

The second bypass passage 200 in which the on-off valve 201 is arranged is located upstream of the merger 29 and in the compression chamber B.
May be communicated with a portion downstream of the switching valve 24 and a portion up to the suction chamber A.

Further, at least in the idling state, the air-fuel mixture is supplied to the combustion chamber S even through the bypass pipe 27. However, the switching valve 24 is switched when the accelerator position (ie, load) is lower than the middle load range. The mixture may be supplied to the combustion chamber S through the bypass pipe 27. In this case, in the case where the second bypass passage 100 is provided, the on-off valve 201 is switched to open in synchronization with the switching operation of the switching valve 24.

In the present embodiment, the carburetor 2
5, the carburetor 25 'or the fuel injector 25 "is provided in the middle of the second pressurized suction pipe 32, as shown by a chain line in FIG. In this case, only fresh air is compressed by the connecting rod supercharging mechanism in the crank chamber 8.

[0051]

As is apparent from the above description, according to the present invention, under a predetermined load, fresh air or air-fuel mixture is directly supplied to the combustion chamber by bypassing the crank chamber. The temperature of the fresh air or mixture does not rise,
A stable output can be derived.

Further, under a predetermined load, the fresh air or the air-fuel mixture bypasses the crankcase, so that the lubricating oil in the crankcase does not flow out of the crankcase together with the fresh air or the air-fuel mixture. The effect of being able to keep it low is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a unit swing type engine unit showing a configuration of a crankcase supercharged four-cycle engine including an intake device according to the present invention.

FIG. 2 is a cross-sectional perspective view showing a configuration of a connecting rod supercharging mechanism of a crankcase supercharged engine including an intake device according to the present invention.

FIG. 3 is a partial cross-sectional view showing a configuration of a merging portion of the intake device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crank chamber supercharged 4-cycle engine 8 Crank chamber 24 Three-way valve (switching means) 27 Bypass pipe (Bypass passage) 34 Reed valve (Check valve) 35 Actuator 23, 26 Suction pipe 28, 32 Pressurized suction pipe 30 Pressure accumulation Chamber 38 Engine Control Unit (ECU) S Combustion Chamber

Claims (6)

[Claims] 1. An intake device for a crankcase supercharged four-stroke engine which compresses fresh air or air-fuel mixture introduced into a crankcase in a crankcase and guides the compressed air or air-fuel mixture into a combustion chamber. A crankcase-supercharged four-stroke engine, comprising: a bypass passage for bypassing the fuel cell and leading to a combustion chamber; and switching means for switching a fresh air or air-fuel mixture introduction path to the bypass passage side under a predetermined load. Intake device. 2. A four-stroke crankcase supercharged engine according to claim 1, wherein a check valve is provided in the bypass passage to allow only a flow of fresh air or air-fuel mixture toward the combustion chamber. Intake device. 3. A four-cycle crankcase supercharging system according to claim 1, wherein said switching means is driven by an actuator whose drive is controlled based on an engine speed or a throttle opening. Engine intake device. 4. The switching means according to claim 1, wherein said switching means comprises a three-way valve provided at a branch where said bypass passage branches from a suction pipe for introducing fresh air or air-fuel mixture into a crank chamber. , 2 or 3, the intake device of a crankcase supercharged 4-cycle engine. 5. A crank according to claim 1, wherein a pressure accumulating chamber is provided in the middle of a pressurized suction pipe for guiding fresh air or air-fuel mixture compressed in the crank chamber to the combustion chamber. An air intake system for a room supercharged 4-cycle engine. 6. The switching means is controlled so that fresh air or air-fuel mixture is introduced into the crank chamber at high rotation speed and high load, and is also introduced into the bypass passage. 3. An intake device for a crankcase supercharged 4-cycle engine according to 3.